At the start of the film, the Batman Squad are still on a mission to capture Batman, but when Bane and his mercenaries attack and take over the city, the police force becomes almost none existent.
Joseph Gordon-Levitt's character, Blake, is one of the more pro-active police officers who wants to fight Bane's mercenaries, but no police officer will stand up to them after Bane put Gordon in the hospital.
Batman's return, and also Matthew Modine's character, inspire the rest of the force to take back their city from Bane.
This eventually starts with smaller attacks on Bane's forces before an all out battle at the film's climax takes place.
Batman, with the help of Catwoman, are trying to stop Bane and a revealed Talia al Ghul from destroying the city and finishing her father's work of destroying Gotham.